male genital system 130 Male 94 rat 76 animal experiment 62 endocrine system 60 nonhuman 58 Rats 52 Animal 48 Support, Non-U.S. Gov't 44 epididymis 42 radioisotope 42 article 40 Testosterone 36 testosterone 34 Animalia 30 Animals 30 animal cell 30 priority journal 30 Castration 28 Epididymis 28 unclassified drug 28 Rats, Inbred Strains 24 androgen 22 castration 22 human 22 human cell 22 in vitro study 22 male 22 Female 18 Human 18